The invention relates to an optoelectronic semiconductor device--often referred to as device hereinafter for short--comprising a semiconductor diode laser--often referred to as laser hereinafter for short--which at a first side thereof emits a first radiation beam with a first wavelength and which forms a radiation waveguide for a second radiation beam with a second wavelength greater than the first wavelength, which second beam can enter the laser at the first side, and a semiconductor photodiode--often referred to as photodiode hereinafter for short--which is present at a second side of the laser opposed to the first side, which is aligned relative to the laser, and which is sensitive to radiation of the second wavelength. The invention also relates to a system for optical glass fibre communication comprising such a device, to a semiconductor diode laser suitable for use in such a device, and to a method of manufacturing such a device.
Such a device is used inter alia as a transmitter/receiver unit at a subscriber who exchanges information via a glass fibre communication network with a central unit or with another subscriber or group of subscribers who are in possession of such a transmitter/receiver unit. The exchanged information may comprise images, sound, and data, such as in the case of telephony, (subscriber) TV, etc., and takes place by means of two kinds of radiation of different wavelengths: radiation with a first wavelength (.lambda..sub.1) for information supplied by the subscriber, and radiation with a second wavelength (.lambda..sub.2) for information to be received by the subscriber or group of subscribers. The transmitter/receiver unit, accordingly, must detect optical signals with the second wavelength and convert them into (conventional) electrical signals, and convert other (conventional) electrical signals into optical radiation signals with the first wavelength.
Such a device is known from U.S. Pat. No. 5,031,188. An optoelectronic semiconductor device is shown therein, for example in FIG. 2 of cited patent, in which a semiconductor diode laser and a photodiode aligned therewith are present in a semiconductor body. The device emits a radiation beam with a wavelength of 1.3 .mu.m at a first side and receives at this same side a radiation beam with a wavelength of 1.5 .mu.m which passes through, in that order, a DFB (=Distributed FeedBack) diode laser which generates the first radiation beam, a monitor and absorption section which is insulated from the diode laser by means of a groove, and an electrical separation zone. Finally, the 1.5 .mu.m radiation reaches a photodiode and is detected thereby. The conversion from electrical into optical signals and vice versa, mentioned above, is achieved by means of the electrical connections of the diode laser and the photodiode.
A disadvantage of the known device is that it is comparatively complicated: it comprises, as the above enumeration shows, comparatively many components which are indeed necessary for a good operation with little crosstalk and interference in the device. It will be clear that the manufacture of such a device is also fairly complicated and comprises many critical steps. This renders the known device comparatively expensive. This disadvantage is especially great because a glass fibre communication system in practice comprises very many such devices, even when one device is shared by a group of subscribers.